Method and device for controlling the limiting of the speed of a vehicle

ABSTRACT

The invention relates to a speed limiter in a vehicle. The speed limiting value which is to be complied with is set by activating a key ( 7 ) on an input device ( 8 ) one or more times. That speed limiting value of the predefined speed limiting values which is the next highest in relation to the current speed of the vehicle is selected. If the current speed of the vehicle is higher than the highest predefined speed limiting value, the speed of the vehicle plus a speed difference is accepted as the speed limiting value. In exceptional situations, the speed limiter can be temporarily suspended, it being possible for an exceptional situation to be, in particular, the upward transgression of the predefined speed limiting value or a (rapid) depression of the gas pedal.

BACKGROUND OF INVENTION

The invention relates to a method for limiting the speed of a vehicle, adevice for carrying out this method and a vehicle having a device ofthis type.

Devices and methods for automatic speed control in vehicles are known.For instance, there are what are referred to as cruise controls that,when activated, maintain the current speed of the vehicle constantlyuntil the driver intervenes in the driving process by activating the gaspedal or the brake, which leads to deactivation of the cruise control.Furthermore, speed limiters are known in which the driver exertscomplete control of the vehicle up to a set speed limiting value and anautomatic intervention into the driving characteristics takes place onlyif the speed approaches the speed limiting value. The intervention isintended to ensure that the predefined speed limiting value is notexceeded and thus to prevent legally prescribed speed limits beingundesirably exceeded.

A system of the type just mentioned is known, for example, from DE 19509 492 A1. In said publication, a particular method is applied in whichan intervention into the driving characteristics already takes placewhen the speed approaches the predefined speed limiting value.

In addition, U.S. Pat. No. 6,076,622 discloses a speed limiter in whichinformation from a distance sensor, which detects when the vehicle isapproaching another vehicle, is additionally taken into account.

Against this background, the object of the present invention is to makeavailable a vehicle with a speed limiter which is easy and reliable tooperate in a variety of driving situations.

SUMMARY OF INVENTION

This object is achieved by means of a method, a device and a vehiclehaving the features of the corresponding independent claims. Thesubclaims contain advantageous refinements.

Firstly, a proposed method for inputting speed limiting values will beexplained in detail for the speed limiter of a vehicle. After anactivation element is activated by the driver of the vehicle, a current,effective speed limiting value v_(lim), which depends on the currentspeed v_(act) of the vehicle, is set.

It is important for the convenience and the reliability of a speedlimiting system that the driver can prescribe desired speed limitingvalues in a simple and intuitive fashion. This objective is achievedwith the proposed method because the current speed of the vehicle istaken into account in the evalution of the activation of the activationelement. As a result, it is possible to react in a way that is matchedto an optimum degree to the input by the driver. This makes the systemconsiderably easier to operate because the settings that areinappropriate for the situation/speed of the vehicle are automaticallyexcluded and the settings that correspond best to the prevailingsituation/speed of the vehicle can be adopted with maximum preference.Simplifying the process in which the system is operated in this wayserves not only to improve convenience but also safety because becausethe risk of incorrect settings is reduced and the driver is notdistracted from the events on the road by awkward inputting procedures.

The selection of a current speed limiting value v_(lim) after theactivation element has been activated can take place, for example, insuch a way that, if possible, the next highest predetermined speedlimiting value in relation to the current speed v_(act) of the vehicleis selected. Which speed limiting values are predefined for selectiondepends, in particular, on the respective legal provisions. Thus, inGermany, there is usually a speed limiting value v₃₀=30 km/h forresidential areas and a speed limiting value v₅₀=50 km/h for built-upareas. If appropriate, a single speed limiting value can also bepredefined for “selection”. In the proposed selection method, that speedlimiting value which is closest to the current speed of the vehicle andat the same time higher than it is automatically searched for. In thespecified example, given a speed v_(act) of a vehicle of 20 km/h, thelimiting value v₃₀ would thus be selected, and given a speed v_(act) ofa vehicle of 35 km/h the limiting value v₅₀ would thus be selected. Ifthe speed v_(act) of the vehicle should happen to be above the maximumpredefined speed limiting value v₅₀, the proposed selection methodcannot be applied. In this case, a suitable alternative selection, forexample that of the highest, predefined speed limiting value v₅₀, mustbe made. An alternative embodiment is explained in more detail below.

The method for selecting a speed limiting value from a predefined set ofa plurality of speed limiting values can be developed in such a way thatthe respective next highest speed limiting value from the series ofpredefined speed limiting values can be adopted as the current speedlimiting value by means of repeated activations of the activationelement in close succession. Accordingly, during the first activation ofthe activation element, a first speed limiting value of the predefinedspeed limiting values is selected, which can be, as explained, the nexthighest value in relation to the current speed of the vehicle. However,if the driver does not wish to retain this value, he can cause the nexthighest of the predefined speed limiting values to be set as theeffective speed limiting value by activating the activation key againwithin a predefined time interval after the first activation. If thisspeed limiting value is not the desired speed limiting value either, itis possible, by activating the activation key once more, which againmust be done within the predefined time interval after the lastactivation, to make a further jump to the next highest speed limitingvalue and so on until the desired limiting speed is set.

If the maximum predefined speed limiting value should happen to bereached in the method just explained and if a renewed activation of theactivation element should happen to take place within the predefinedtime interval after the last activation, said renewed activation ispreferably interpreted as being a command for deactivation of the speedlimiter so that a corresponding signal is generated.

Furthermore, a signal for deactivating the activated speed limiter canbe generated if the predefined time interval mentioned above since thelast activation of the activation element has expired and the activationelement is activated again after that.

The activation element serves, on the one hand, to set a desired speedlimiting value and, if appropriate, to activate the speed limiter. Onthe other hand, it serves simultaneously to deactivate the speed limiterif it is no longer desired. It thus becomes possible for a singleactivation element to be used for the entire operator control of thislimitation process, said element reacting suitably to its activationdepending on the situation. This not only provides greater convenienceand makes the system easier to operate but also considerably improvesthe safety. The driver can in fact activate the activation elementwithout looking because it is not a case of selecting one key of severalor one specific position setting.

According to one embodiment of the proposed method, after the activationelement has been activated, the current speed v_(act) of the vehicleincreased by a speed difference Δv is set as the current speed limitingvalue v_(lim), i.e., v_(lim)=v_(act)+Δv. Similarly to a cruise control,the driver can thus set the vehicle to a specific speed and predefinesaid speed to the automatic system at a guideline value. However, incontrast to a cruise control, no attempt is made to maintain this speedconstantly but rather the automatic system merely ensures that the setspeed is not exceeded. Such an adoption of a speed of the vehicle as aspeed limiting value is possible in combination with the use ofpredefined speed limiting values as explained above: if the vehicle isat a vehicle speed below the maximum predefined speed limiting valuewhen the activation element is activated, said limiting value or acorrespondingly lower speed limiting value can be adopted. On the otherhand, if the speed of the vehicle is higher than the highest availablepredefined speed limiting value, the previously explained method of theadoption of the current speed of the vehicle as a guideline value isapplied. In this way, any desired limiting value can be set in anapproximated fashion at higher speeds (for example for limiting thespeed of the vehicle to 100 km/h on country roads).

The speed difference Δv can be treated as a predefined constant.However, it is preferably selected, taking into account theinstantaneous acceleration of the vehicle, in such a way that the speedof the vehicle cannot exceed the set speed limiting value v_(lim) untilthe speed limiter becomes effective. This prevents the situation inwhich, when the activation element is activated, the current speed ofthe vehicle which is adopted as the speed limiting value is one which isexceeded just a short time later due to the current acceleration of thevehicle, the upward transgression of the limiting value taking placebefore the speed limiter can become active and effective. The speeddifference Δv thus constitutes a safety margin for the functioning ofthe speed limiter.

According to one embodiment of the method, a signal for reactivating thedeactivated speed limiter is generated if the activation element isactivated. This means that the switched-off speed limiter is alsoswitched on again by means of the activation element. The activationtakes place if the activation element is activated once or if it isactivated repeatedly in succession, in which case however there cannotbe more than one predefined time interval between individualactivations.

Furthermore, a signal for deactivating the activated speed limiter ispreferably generated if the vehicle is switched off. This ensures thatwhenever the vehicle starts, the speed limiter is in the deactivatedstate.

An input device is also proposed for inputting speed limiting values fora speed limiter of a vehicle. This device has at least one activationelement which can be operated by the driver, and a signal input fortransmitting a signal which indicates the current speed v_(act) of thevehicle. Furthermore, the input device is configured in such a way thatit can carry out a method of the type explained above. After theactivation element has been activated, a current speed limiting valuev_(lim),which depends on the current speed v_(act) of the vehicle, isthus set by the input device.

Moreover, a method for limiting the speed of a vehicle is proposed inwhich, as measures for complying with a predefined speed limiting valuev_(lim), it is preferable to reduce the power of the propulsion unitand/or the torque of the propulsion unit of the vehicle and/or toimplement a braking torque if the current speed v_(act) of the vehicleapproaches the predefined limiting value v_(lim) or exceeds it. Themethod is defined in that the aforesaid measures for limiting the speedare temporarily suspended in exceptional situations. On the other hand,after the exceptional situation passes, the measures, and thus the speedlimitation, are re-applied if the above preconditions for theiractivation still apply.

Taking into account exceptional considerably increases the safety of thespeed limitation in traffic because in an emergency the driver still hascomplete control of the vehicle without having to deactivate the speedlimiter himself in advance. In exceptional situations, there is in factno time for such a deactivation initiated by the driver. In addition,such deactivation can easily be forgotten under stressful conditions.

There are various possibilities for the definition of exceptionalsituations which lead to the speed limiter being suspended. According toa first variant, an exceptional situation occurs if the current speedv_(act) of the vehicle exceeds the instantaneously predefined speedlimiting value v_(lim) by more than a predefined speed excess v_(extra):

v_(act)>v_(lim)+v_(extra). Such an exceptional situation can occur ifthe measures taken by the speed limiter were not able to prevent thepredefined speed limiting value v_(lim) from being exceeded. This may bethe case, for example, when the vehicle is traveling downhill. As soonas the speed is exceeded in such a way, the measures for limiting thespeed are suspended so that the driver is given sole, unaffected controlof the vehicle. In this way, it is possible to avoid, for example,skidding when traveling down extreme inclines, which could occur as aresult of excessively severe deceleration interventions by the speedlimiter.

In the case just explained, the measures for limiting the speed arepreferably incrementally reduced as the amount the speed v_(act) of thevehicle exceeds the set speed limiting value v_(lim) is increased. Ifthe speed v_(act) of the vehicle lies above the speed limiting valuev_(lim) by the abovementioned speed excess v_(extra), the measures forlimiting the speed are completely switched off. This ensures that thespeed limitation is continuously reduced from 100% to 0% in a range ofthe speed of the vehicle between the predefined speed limiting valuev_(lim) and a value which is higher by the speed excess v_(extra).Conversely, when the speed of the vehicle is decreased, there is acorresponding continuous graduated implementation of the measures forlimiting the speed limitation. This ensures that an abrupt transitionbetween the activation and the suspension of the speed limiter, whichcould adversely affect the driving characteristics of the vehicle, doesnot take place.

According to another refinement of the method, an exceptional occurs ifthe position s of the gas pedal and/or the rate ds/dt of the change inposition of the gas pedal fulfill a predefined criterion, which pointsto the request for a high acceleration. Thus, it may, for example, bethe case that the driver briefly wishes to effect a maximum accelerationof the vehicle and upward transgression of the predefined speed limitingvalue during an overtaking procedure or in order to avoid a criticalsituation. This would not be possible with the speed limiter activatedbecause it would actually attempt to prevent the predefined speedlimiting value being exceeded. Accordingly, the driver would have toexplicitly deactivate the speed limiter in advance by means of acorresponding operating procedure, which is not only awkward andtime-consuming in an emergency situation but is also easily forgotten.For this reason, it is proposed that the observed position and/or rateof the change in position of the gas pedal be taken as a starting pointthat the driver wishes a maximum acceleration of the vehicle. Duringdetection of such a state, the speed limiter can then be automaticallysuspended until the criteria for the exceptional situation are no longerfulfilled.

The criterion for the presence of an exceptional situation can consist,for example, in a case when the position s of the gas pedal is beyond apredefined limiting position s_(lim). Thus, an exceptional can beadopted, for example, if the position s of the gas pedal lies between95% and 100% of the activation travel. In addition, or alternatively,the rate ds/dt of the change in position of the gas pedal can also beused during the detection of an exceptional situation. Here, rapiddepression of the gas pedal indicates, through a high rate in the changein position, that a maximum acceleration of the vehicle is expected tobe required. Therefore, to detect the exceptional it is not necessary towait until the gas pedal has been depressed beyond a limiting position.

The activation and/or deactivation of the measures for limiting thespeed are/is preferably carried out continuously. In this way, abrupttransitions which could have an adverse effect on the drivingcharacteristics of the vehicle, are avoided.

Furthermore, a control device for limiting the speed of a vehicle isproposed. This device contains an apparatus for reducing the power ofthe propulsion unit and/or the torque of the propulsion unit and/or forimplementing the braking torque. This apparatus is activated if thecurrent speed v_(act) of the vehicle approaches a prescribed speedlimiting value v_(lim) or exceeds it. The control device is defined inthat it is configured to carry out a method of the type explained above.That is to say that in the case of exceptional situations the controldevice temporarily suspends the speed limiting measures. The type ofexceptional and their handling can correspond to the variants of themethod explained above.

The invention also relates to a vehicle having a propulsion unit and aninput device for inputting speed limiting values for a speed limiter andhaving a control device, coupled to the input device, for limiting thespeed of the vehicle. The input device and/or the control device can beimplemented here as one of the types explained above.

In this vehicle, the input device preferably contains a display whichindicates the operating states of the control device to the driver. Inparticular, it is possible to indicate whether the control device isswitched on or off or whether its activity is temporarily suspendedowing to an exceptional state. The suspension in the case of anexceptional state is preferably indicated by means of a particularlyconspicuous form of indication such as flashing.

The vehicle can have in particular an internal combustion engine and/oran electric motor as its propulsion unit. The use of an electric motoris preferred because it can also be used to implement a braking torquewhich actively supports the speed limitation in its task of preventing aspeed limiting value from being exceeded.

BRIEF DESCRIPTION OF DRAWINGS

The invention is explained in more detail below by way of example withreference to the figures, in which:

FIG. 1 is a schematic view of the components of a vehicle with a speedlimiter;

FIG. 2 shows a diagram relating to the graduated activation anddeactivation of measures for limiting the speed when the predefinedspeed limiting value is exceeded;

FIG. 3 shows a diagram with the state transitions of the speed limiter.

DETAILED DESCRIPTION

FIG. 1 is a schematic view of the components of a vehicle with which asystem for speed limitation is implemented. The vehicle has a drivesystem which is composed of the propulsion unit 1 and the wheels 5 whichare connected to the propulsion unit, if appropriate via a gearmechanism. In the case illustrated, the propulsion unit 1 is intended tobe an electric motor, but the following embodiments also apply similarlyfor the use of an internal combustion engine.

The propulsion unit 1 is regulated by a propulsion unit regulator 2(TIM). The propulsion unit regulator 2 is in turn connected via abidirectional connecting line 4 to a vehicle system regulator 3 (VSC),which is responsible for the entire coordination of the transmissionpower, for the interaction with the driver and the like.

Although the propulsion unit regulator 2 and the vehicle systemregulator 3 are illustrated as two physically separate systems in FIG.1, they can also be accommodated in the same physical control unit. Inthis case, the connection 4 would be, for example, a pure softwareinterface. The illustrated system is, however, usually arrangeddistributed over the entire vehicle. The communication between thepropulsion unit regulator 2 and the vehicle system regulator 3 thereforerequires a physical communication connection 4, such as a standardizedController Area Network (CAN), for example.

The acceptable vehicle speed is increasingly limited by legalrequirements. In Europe, the speed limits of 30, 50 or 70 km/hfrequently apply. With the high-performance or high-torque propulsionunits which are increasingly common, such speed limits can be exceededeven with slight pressure on the gas pedal. In order to prevent this,the speed limiting function described in more detail below is used.

When a speed limiting function is designed, a plurality of aspects areto be considered. For example, a torque limiter which is to beimplemented in a simple way for the propulsion unit is not expedient inall possible situations because the torque and the speed of the vehicleare related to one another via the tractive resistance. For this reason,a higher torque is required, for example given the same speed whentraveling uphill than when traveling on the flat.

Furthermore, it is desirable if no rigid limitation of the speed isimplemented but rather if the driver retains the possibility oftemporarily exceeding the speed limiting value in emergencies in order,for example, to be able to reliably carry out an overtaking maneuver.Moreover, it is desirable for the convenience and the prevention ofoperating errors if the interface between the system and the driverfunctions as simply, reliably and transparently as possible.

Finally, when the vehicle control is divided similarly to that shown inFIG. 1, it is necessary to ensure that the respective control functionsare unambiguously assigned to the modules and that communication cantake place, for example, via a CAN.

In order to achieve the abovementioned objectives, the vehicle systemregulator 3 illustrated in FIG. 1 is additionally equipped with an inputfunction, while the propulsion unit regulator 2 is given the additionalfunction of a speed limiter. Firstly, the function of the input device 8will be explained in more detail.

The interface with the driver which is formed at the input device 8comprises essentially a knob 7 which the driver can activate bypressing, and a signal lamp 6 (LED). By activating the knob 7 one ormore times, the driver can make various settings relating to the speedlimitation. The reaction of the input device 8 to an activation of theactivation element 7 depends-here essentially on the current vehiclespeed v_(act), which is communicated to the input device 8 via signallines 4 from the propulsion unit regulator 2. The following table givesthe reactions of the input device 8 to activations of the key 7 forvarious speeds v_(act) of the vehicle:

Vehicle speed v_(act) [km/h] <30 <50 >50 Action Signal 6 selectedv_(lim) [km/h] 1) Start of vehicle off — — — 2) Driver presses key 7 on30 50 v_(act) + Δv 3) Driver presses key 7 on 50 50 v_(act) + Δv brieflyagain after 2) 4) Driver presses key 7 for a off — — — relatively longtime after 2) or 3) or driver presses key 7 again briefly after 3)

When the vehicle is started by turning the ignition key, the speedlimiting function is thus disabled, for which reason the signal lamp 6remains unlit. The driver has complete control of the torque and theperformance of the power transmission. If the driver presses the key 7once, the speed limiter is activated, and a value which depends on thecurrent speed v_(act) as follows is defined as the speed limiting value:If v_(act) is lower than 30 km/h, the speed limiting value is set to 30km/h. If the v_(act) is between 30 km/h and 50 km/h, the speed limitingvalue is set to 50 km/h. On the other hand, if v_(act) is above 50 km/h,the speed limiting value is set to the current vehicle speed v_(act)plus a speed difference Δv. Δv can be calculated in different ways. Inthe simplest case, Δv is constant, for example Δv=5 km/h. An advancedapproach comprises taking into account the instantaneous vehicleacceleration in order to increase or reduce Δv correspondingly. Thepurpose of Δv is to prevent the speed of the vehicle exceeding the setspeed limiting value particularly in the phase during which the speedlimiter switches over from the deactivated state to the activated state.

As is also apparent from the table, when the key 7 is activatedrepeatedly, a distinction is made as to whether the activations takeplace in rapid succession or whether a predefined time interval isexceeded between two activations.

The function of the speed limiter which is implemented in the propulsionunit regulator 2 will be described in more detail below. The speedlimiter can be activated or deactivated, which takes place in the wayexplained above by means of the input device 8. If the speed limiter isbasically activated, it monitors the state of the vehicle and engages inthe driving process if the current speed v_(act) of the vehicle and theposition s of the gas pedal fulfills specific criteria. Firstly, theeffect of the current speed v_(act) of the vehicle will be considered.

The current speed v_(act) of the vehicle is usually below the set speedlimiting value v_(lim). An intervention of the speed limiter is notnecessary if it is active in a basic monitoring mode because acorresponding activation flag has been transmitted by the input device8.

If the driver then attempts to accelerate the vehicle beyond thepredefined speed limiting value v_(lim), the propulsion unit regulator 2reduces or limits the torque in such a way that the speed limiting valueis not exceeded. Here, a braking torque can preferably also beimplemented if this is possible, for example as in the case of theelectric motor 1.

When traveling downhill for example, it is possible for a situation tooccur in which the speed limiter is not capable of keeping the speed ofthe vehicle below the predefined speed limiting value. If the speed ofthe vehicle then exceeds the speed limiting value v_(lim), the state ofthe speed limiter is changed from ACTIVE to SUSPENDED. The correspondingtransition is illustrated in FIG. 2, the current speed v_(act) of thevehicle being represented on the horizontal axis and the maximumpermitted braking torque T being represented on the vertical axis. As isapparent from the diagram, the maximum torque T which can be appliedafter the speed limiting value v_(lim) has been exceeded is reduced from100% in a ramp shape to 0%, or “deactivated in a graduated fashion”, thecomplete deactivation taking place at the speed v_(lim)+v_(extra).Beyond this speed, the speed limiter is therefore no longer effectiveand the driver has sole control of the vehicle. If the speed v_(act) ofthe vehicle is then reduced again, in the reversal of this process themaximum torque T which can be applied, and thus the speed limiter isthen “activated again in a graduated fashion” continuously from 0% to100%. Below the speed limiting value v_(lim), the state of the speedlimiter then changes again from SUSPENDED to ACTIVE.

The described characteristics thus take into account an exceptionalwhich comprises the predefined speed limiting value v_(lim) beingexceeded, the measures of the speed control being deactivated andactivated in a gradual transition during the exceptional situation.

A further exceptional is defined by means of the state of the gas pedal.The position s of the gas pedal is expressed here, for example, by meansof a standardized value between 0% and 100%, s=100% corresponding to acompletely depressed gas pedal. If the position s of the gas pedal isbelow a predefined limiting value s_(lim), the speed limitation is notinfluenced. However, in the case of an emergency situation it ispossible that the driver requires a maximum torque and would like toexceed the predefined speed limiting value. For this reason, thefunction of the speed limiter is temporarily suspended if the position sof the gas pedal exceeds the predefined threshold s_(lim). The limitingvalue s_(lim) can be predefined here or calculated during driving.

In addition, the rate ds/dt of change of the position s can be used inorder to permit a more rapid response and identification of theexceptional situation. During the exceptional situation which isindicated by means of the gas pedal, the speed limiter is switched overfrom the ACTIVE state to the SUSPENDED state in a way similar to thatexplained above for the speeds of the vehicle.

By means of appropriate filtering such as, for example, a P-T1 filter,it should be ensured here that the torque does not make a jump when thesuspension occurs. Such a jump would take place if a reduction in thetorque which then suddenly dropped away subsequently were implemented bythe speed limiting function up to the point where the pedal positions_(lim) is reached.

FIG. 3 shows a state diagram for the speed limiter which is implementedin the propulsion unit regulator 2. The speed limiter changes into theswitched-on ACTIVE state from the switched-off INACTIVE state if anactivation flag is set by the input device 8 (FIG. 1) and the vehicle isstarted.

As has been explained above, the ACTIVE state is temporarily exited inexceptional situations by going into the SUSPENDED state. Such atransition takes place if the current speed v_(act) of the vehicle ishigher than the prescribed speed limiting value v_(lim) or if theposition s of the gas pedal exceeds a limiting value s_(lim). If theaforesaid conditions already apply when the INACTIVE state is exited, atransition into the SUSPENDED state from there takes place immediately.

As soon as the preconditions for the SUSPENDED state no longer apply,said state is exited by jumping back into the ACTIVE state. In thiscontext, the combined monitoring of the gas pedal position and of thepedal speed together with the monitoring of the vehicle speed provesparticularly advantageous (even if both monitoring criteria can alsoonly be implemented individually): for example, in order to initiate anacceleration process due to overtaking, the gas pedal is firstlydepressed or activated very rapidly so that there is a transition to theSUSPENDED state. The acceleration results in a speed of the vehiclewhich frequently lies above v_(lim) so that the SUSPENDED state isfirstly still retained even when the gas pedal is released, and thesystem changes unnoticeably and continuously back to the ACTIVE state asthe speed drops.

If the activation flag for the speed limiter is cancelled by the inputdevice 8 or if the vehicle is switched off, a jump back into theINACTIVE state from the ACTIVE or SUSPENDED states takes place.

The transitions which are illustrated in the state diagram of FIG. 3 areimplemented in such a way that they take place continuously and withoutabrupt transitions in the behavior of the vehicle.

A typical use scenario for the speed limiter according to FIG. 1 isdescribed below. Firstly, the driver activates the speed limitingfunction by activating the key 7. The input device 8 then reads thecurrent vehicle speed v_(act) and calculates the speed limiting valuev_(lim). The latter is transmitted to the propulsion unit regulator 2together with an activation request. The propulsion unit regulator 2then controls the propulsion unit, using positive and negativepropulsion unit torques, in such a way that the predefined speedlimiting value v_(lim) is not exceeded.

The input device 8 also transmits the limiting value s_(lim) for theposition of the accelerator pedal, which limiting value s_(lim) is usedby the propulsion unit regulator 2 to switch over into the SUSPENDEDstate if appropriate.

The states of the speed limiter illustrated in FIG. 3 are transmitted tothe input device 8 via the connection 4. The respective state is thensymbolized by the signal lamp 6 in accordance with the following tablein order to inform the driver of the function of the speed limiter.

State Signal lamp ACTIVE on INACTIVE off SUSPENDED flashing

The communication between the input device 8 and the speed limiter 2takes place via the communications interface 4. The latter isrepresented by a set of variables which are transmitted either via aphysical communications connection (for example CAN) or via a puresoftware interface. The following data formats are typically used here:

Signals from the input device 8 to the propulsion unit regulator 2:

a) Speed limiting value v_(lim):

1-byte variable, resolution 1 km/h;

b) Speed limiter active:

1-byte flag, AAh=TRUE, 00=FALSE;

Communication from the propulsion unit regulator 2 to the input device8:

a) Status of the speed limiter:

1-byte variable, states: INACTIVE, ACTIVE, SUSPENDED.

While certain embodiments of the present invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention as defined by the following claims.

What is claimed is:
 1. A method for limiting the speed of a vehiclecomprising: providing a speed limiting device, providing a plurality ofpre-set speed limiting values to said speed limiting device, whereinsaid plurality of pre-set speed limiting values are vehicle speed valuesof the vehicle, activating said speed limiting device, and firstactuating an activation element, said first actuating causing a firstspeed limiting value of said plurality of pre-set speed limiting valuesto be input to said speed limiting device, whereby said speed limitingdevice begins regulating the speed of said vehicle such that the speedof said vehicle remains at or below said first speed limiting valueuntil said speed limiting device receives a further input.
 2. The methodof claim 1, wherein said first speed limiting value is both higher thanand, of said plurality of pre-set speed limiting values, closest to saidspeed of said vehicle at the moment of said first actuating.
 3. Themethod of claim 2, further comprising the step of second actuating saidactivation element within a first time interval after said firstactuating, said second actuating deactivating said speed limiting devicewhen there is no second speed limiting value of said plurality ofpre-set speed limiting values that is higher than said first speedlimiting value.
 4. The method of claim 2, further comprising the step ofsecond actuating said activation element within a first time intervalafter said first actuating, said second actuating causing a second speedlimiting value of said plurality of pre-set speed limiting values to beinput to said speed limiting device, wherein said second speed limitingvalue is both higher than and, of said plurality of pre-set speedlimiting values, closest to said first speed limiting value, whereby thespeed of said vehicle remains at or below said second speed limitingvalue until said speed limiting device receives a further input.
 5. Themethod of claim 2, wherein said first speed limiting value is furtherrelated to a speed difference.
 6. The method of claim 5, wherein saidspeed difference is related to the acceleration of said vehicle at themoment of first actuating, such that said vehicle does not exceed saidfirst speed limiting value before said first speed limiting value isinput to said speed limiting device.
 7. The method of claim 1, furthercomprising the step of further actuating said activation element,outside of a first time interval after said first actuating, wherebysaid further actuating causes said speed limiting device to bedeactivated.
 8. The method of claim 1, wherein the step of activatingsaid speed limiting device is accomplished by said first actuating anactivation element.
 9. The method of claim 1, further comprising thestep of deactivating said speed limiting device when said vehicle isturned off.
 10. The method of claim 1, further comprising the step ofentering a suspend mode, said suspend mode causing said further input tobe received by said speed limiting device, whereby said speed limitingdevice allows the speed of said vehicle to exceed said first speedlimiting value.
 11. The method of claim 10, further comprising the stepof exiting said suspend mode, whereby said speed limiting device resumessaid regulating the speed of said vehicle such that the speed of saidvehicle remains at or below said first speed limiting value until saidspeed limiting device receives a further input.
 12. The method of claim10, wherein said step of entering a suspend mode occurs when the speedof said vehicle exceeds said first speed limiting value.
 13. The methodof claim 10, wherein said step of entering a suspend mode occurs when avehicle accelerator exceeds a pre-determined position limit.
 14. Themethod of claim 10, wherein said step of entering a suspend mode occurswhen the position of a vehicle accelerator changes at a rate thatexceeds a pre-determined position change rate limit.
 15. The method ofclaim 10, wherein the step of said speed limiting device allows thespeed of said vehicle to exceed said first speed limiting value isaccomplished gradually.
 16. The method of claim 1, further comprisingthe step of providing a first display to a driver of said vehicle toindicate that said speed limiting device is activated.
 17. The method ofclaim 16, further comprising the step of providing a second display tosaid driver of said vehicle to indicate said speed limiting device is ina suspend mode.
 18. A method for limiting the speed of a vehiclecomprising: providing a speed limiting device, providing a plurality ofpre-set speed limiting values to said speed limiting device, whereinsaid plurality of pre-set speed limiting values are vehicle speed valuesof the vehicle, activating said speed limiting device, and firstactuating an activation element, said first actuating causing a firstspeed limiting value to be input to said speed limiting device as atleast one of said plurality of pre-set speed limiting values, said firstspeed limiting value being related to the speed of said vehicle at themoment of first actuating, whereby said speed limiting device beginsregulating the speed of said vehicle such that the speed of said vehicleremains at or below said first speed limiting value until said speedlimiting device receives a further input.
 19. The method of claim 18,wherein said first speed limiting value is further related to a speeddifference.
 20. The method of claim 19, wherein said speed difference isrelated to the acceleration of said vehicle at the moment of firstactuating, such that said vehicle does not exceed said first speedlimiting value before said first speed limiting value is input to saidspeed limiting device.
 21. The method of claim 18, further comprisingthe step of further actuating said activation element, outside of afirst time interval after said first actuating, whereby said furtheractuating causes said speed limiting device to be deactivated.
 22. Themethod of claim 18, wherein the step of activating said speed limitingdevice is accomplished by said first actuating an activation element.23. The method of claim 18, further comprising the step of deactivatingsaid speed limiting device when said vehicle is turned off.
 24. Themethod of claim 18, further comprising the step of entering a suspendmode, said suspend mode causing said further input to be received bysaid speed limiting device, whereby said speed limiting device allowsthe speed of said vehicle to exceed said first speed limiting value. 25.The method of claim 24, further comprising the step of exiting saidsuspend mode, whereby said speed limiting device resumes said regulatingthe speed of said vehicle such that the speed of said vehicle remains ator below said first speed limiting value until said speed limitingdevice receives said further input.
 26. The method of claim 24, whereinsaid step of entering a suspend mode occurs when the speed of saidvehicle exceeds said first speed limiting value.
 27. The method of claim24, wherein said step of entering a suspend mode occurs when a vehicleaccelerator exceeds a pre-determined position limit.
 28. The method ofclaim 24, wherein said step of entering a suspend mode occurs when theposition of a vehicle accelerator changes at a rate that exceeds apre-determined position change rate limit.
 29. The method of claim 24,wherein the step of said speed limiting device allows the speed of saidvehicle to exceed said first speed limiting value is accomplishedgradually.
 30. The method of claim 18, further comprising the step ofproviding a first display to a driver of said vehicle to indicate thatsaid speed limiting device is activated.
 31. The method of claim 30,further comprising the step of providing a second display to said driverof said vehicle to indicate said speed limiting device is in a suspendmode.
 32. A device for limiting the speed of a vehicle comprising: aspeed control device, an activation element, said activation elementbeing capable of being actuated by a driver of said vehicle, a speedsensor, said speed sensor being capable of ascertaining the speed ofsaid vehicle, a speed limiting value determination device operativelycoupled with said activation element and said speed sensor, said speedlimiting value determination device being capable of receiving aplurality of pre-set speed limiting values, wherein said plurality ofpre-set speed limiting values are vehicle speed values of the vehicle,and of selecting a speed limiting value, and an input transmissiondevice, said input transmission device operatively coupled with saidspeed limiting value determination device and said speed control device,said input transmission device being capable of inputting said speedlimiting value to said speed control device as at least one of saidplurality of pre-set speed limiting values, whereby said speed controldevice begins regulating the speed of said vehicle such that the speedof said vehicle remains at or below said speed limiting value until saidspeed control device receives a further input.
 33. The device of claim32, wherein said speed limiting value is related to the speed of saidvehicle at the moment said activation element is actuated by said driverof said vehicle.
 34. The device of claim 32, further comprising anacceleration sensor operatively coupled with said speed limiting valuedetermination device, said acceleration sensor being capable ofascertaining the rate of acceleration of said vehicle.
 35. The device ofclaim 34, wherein said speed limiting value is related to the speed ofsaid vehicle at the moment said activation element is actuated by saiddriver of said vehicle and the rate of acceleration of said vehicle atthe moment said activation element is actuated by said driver of saidvehicle.
 36. The device of claim 32, further comprising an exceptionalsituation determination unit operatively coupled with said speed controldevice, said exceptional situation determination unit being capable ofgenerating said further input and transmitting said further input tosaid speed control device, whereby said speed control device enters asuspend mode upon receiving said further input wherein said speedcontrol device allows the speed of said vehicle to exceed said speedlimiting value.
 37. The device of claim 36, wherein said exceptionalsituation determination unit generates said further input when the speedof said vehicle exceeds said speed limiting value.
 38. The device ofclaim 36, wherein said exceptional situation determination unitgenerates said further input when a vehicle accelerator exceeds apre-determined position limit.
 39. The device of claim 36, wherein saidexceptional situation determination unit generates said further inputwhen the position of a vehicle accelerator changes at a rate thatexceeds a pre-determined position change rate limit.
 40. The device ofclaim 36, wherein said exceptional situation determination unit signalssaid speed control device to resume said regulating the speed of saidvehicle such that the speed of said vehicle remains at or below saidspeed limiting value until said speed limiting device receives saidfurther input.